A classical logic analyzer is an electronic instrument that captures and displays multiple digital signals from a digital system or digital circuit, hereinafter referred to as device under test, short DUT. A logic analyzer may convert the captured data into timing diagrams, protocol decodes, state machine traces, assembly language, or may correlate assembly with source-level software. Logic analyzers have advanced triggering capabilities and are useful when a user needs to see the timing relationships between a plurality of digital signals generated by the DUT.
At the digital input ports of the MSO a distinct discretization unit is used for each specific digital input port to read the applied measured signal and to sample the value of the applied (digital) signal at that time point. Such a discretization unit might comprise an analog comparator that compares the (digital) input signal with a predefined threshold voltage value in order to decide whether a logic low-state or a logic high-state of the applied (digital) signal is received at the distinct digital input port. It should be noted that the discretization unit of a digital input port of an MSO cannot be compared to the precise and complex analog-to-digital conversion unit arranged at the analog input ports of the MSO to digitize an analog signal, since the MSO expects a digital input signal at the digital input port and thus there is no need to apply a full scale analog-to-digital conversion. Using such a discretization technique has the technical drawback that all amplitude information of the applied signal is lost.
U.S. Pat. No. 5,446,650 describes a better approach for a logic signal extraction with an oscilloscope. Therein, a digital input signal is first sampled as an analog signal to produce multi-bit digital samples that are representative of the amplitude of the input signal over time. The multi-bit digital samples are then processed using interpolative techniques to ascertain when the input signal crossed a hypothetical logic level threshold and when the signal is in a specific logic state.
Current oscilloscope/MSO approaches, however, still present drawbacks with regard to the distortion of the applied signal, and adjustment of a threshold level and compensation for MSO and probe-generated errors and losses.
What is needed, therefore, are approaches for oscilloscopes/MSOs that achieve further improvements in the measurement and analysis of an applied signal (i.e., digital signal) at a respective input port, such as improvements in the reduction in distortion of the applied signal, and in the adjustment of a threshold level and compensation for MSO and/or probe-generated errors and losses.